"My heart is in the East, and I am at the end of the West"
Yehuda Halevi (the Levite) was born in Toledo, then the capital of Castile, in or around 1086. This was during the Muslim rule of Spain, that age which still today the Jews and Muslims call the Golden Age; very different to the Golden Age spoken of by the Christian Spaniards. This was an age of religious freedom, cultural wealth and material prosperity, while European Jews and Eastern Muslims were undergoing the trauma of the Crusades, Castile was relatively untroubled.
Halevi studied under the Isaac Alfasi at Lucena, learning Talmud as well as other disciplines. He became - like many of the time - something of a linguist, speaking Aramaic, Arabic and Hebrew, and also studied medicine, becoming a practicing doctor in Toledo. There he married and, when the pressures of a hectic life got too much, moved with his family to Cordoba.
Poetry
Yehuda Halevi is perhaps most famous as a poet, significant to both Jews and non-Jews alike. Any serious attempt to explore Arab poetry during the Middle Ages takes Halevi into account, even though he wrote largely in Hebrew. His poetry covers a wide variety of topics, some almost erotic, some lamenting, some humorous. Many were directed to individuals like Abraham ibn Ezra, his contemporary. He used common Arab metres and rhythms in his poems, but in a wonderfully fluid way, like he wasn't even trying.
Halevi also wrote overtly religious poetry, some of which has been incorporated into parts of the Jewish liturgy. Some are laments over Jerusalem and the state of the Jewish people; some are love-song to Shabbat. The most well-known of these "Yom Shabbaton" (The Sabbath Day), is one of the songs commonly sung around the Shabbat table by Jewish families today.
Religious Texts and Philosophy
Yehuda Halevi's most significant contribution to Jewish thought is the Kuzari. This work, originally written in Arabic, is a fictionalisation of a real event that took place between the 7th and 9th Centuries, when the King of the Khazars converted to Judaism, along with a number of his people. Halevi imagines the King trying to decide what religion he should be, and inviting a Christian and a Muslim scholar to convince him. When he doesn't like their philosophies, he invites a Jew who explains Judaism to him. The King is so impressed that he converts.
Halevi uses this setup to express, through the Socratic dialogue between the King and the Jew, his own views on Judaism. They are somewhat controversial. He believes Jews are superior to Gentiles by virtue of their birth and the transfer of some sort of divine essence, and that converts can never be equal to 'real' Jews. This position is in stark opposition to Moses Maimonides and most other Jewish thinkers of the time. Apart from this point, though, the Kuzari lays out many of the basics of Jewish belief. Particularly important is his explanation of Jewish nationhood.
proto-Zionism
Halevi remained convinced that the Jewish people shouldn't get too comfortable in Spain. He was committed to the return to Zion and Jerusalem, and some form of Jewish national independence there. In keeping with this belief, after his wife died, he began the difficult journey to Jerusalem, stopping for some time in Alexandria. What happens next is unclear. Some sources say he went to Syria, and travelled from there to Jerusalem. Some say he remained in Alexandria. Evidence from the Cairo Geniza implies he may have left Alexandria by sea, and made it to Jeruslalem before his death. The most common, though unlikely, tale is a legend that he reached Jerusalem, and fell to his knees at the sight of it. There, he recited one of his poems in praise
of the city, only to be run over and killed by an Arab horseman leaving through the gate of the city. He died in about 1140, leaving a rich legacy for future generations.
nasreddin points out that he's often mentioned in The Dictionary of the Khazars
http://www.us-israel.org/jsource/biography/Halevi.html
http://www.wikipedia.com